U.S. Pat. No. 4,239,519 is directed to the preparation of inorganic, crystal-containing gels and papers, fibers, films, boards, and coatings produced therefrom. The method for making the precursor gels involves three fundamental steps: (a) a fully or predominantly crystalline body is formed which contains crystals consisting essentially of a lithium and/or sodium water-swelling mica selected from the group of fluorhectorite, hydroxyl hectorite, boron fluorphlogopite, hydroxyl boron phlogopite, and solid solutions between those and other structurally-compatible species selected from the group of talc, fluortalc, polylithionite, fluorpolylithionite, phlogopite, and fluorphlogopite; (b) that body is contacted with a polar liquid, normally water, to cause swelling and disintegration of the body accompanied with the formation of a gel; and (c) the solid:liquid ratio of the gel is adjusted to a desired value depending upon the application therefor. Glass-ceramics are the preferred crystalline starting bodies.
To impart good chemical durability to papers, films, fibers, boards, and coatings prepared from the gels, those products are contacted with a source of large cations to cause flocculation of the gel and an ion exchange reaction to take place between the large cations and the Li.sup.+ and/or Na.sup.+ ions from the interlayer of the crystals, and then washed and dried. As illustrative of large cations operable in that ion exchange reaction, the patent cites K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Cu.sup.+, Ag.sup.+, H.sub.3 O.sup.+, Ca.sup.+.spsp.2, Sr.sup.+2, Ba.sup.+2, Pb.sup.+.spsp.2, and certain organic polycations, e.g., aniline hydrochloride and quaternary ammonium compounds. If desired, the ion exchange reaction may be undertaken with the gel, i.e., before a paper, fiber, film, board, coating, or other product is made, or during the process for actually forming the product. In any event, wherever the ion exchange step is conducted in the stream of production, its occurrence is mandatory to preclude spontaneous disintegration of the products in the presence of water.
Long term testing of products made in accordance with the disclosure of that patent has indicated that the values of such physical properties as mechanical strength, flexibility, dielectric strength, loss tangent, and ionic conductivity are influenced by the relative humidity of the surrounding environment. Stated differently, the properties displayed by the products are not stable. In the main, there is an overall deterioration in the mechanical and electrical properties as the relative humidity of the atmosphere is increased.
Consequently, the primary objective of the instant invention is to devise means for rendering papers, films, boards, fibers, and coatings prepared in accordance with the disclosure of U.S. Pat. No. 4,239,519, supra, relatively insensitive to the relative humidity of the environment in which the product will be used.